Severe idiopathic inflammatory myopathies (polymyositis, dermatomyositis, and related diseases) that respond poorly to corticosteroids are difficult to treat. We have undertaken three therapeutic trials for the treatment of such patients: a) a controlled double-blind trial of phasmapheresis and leukapheresis; b) a controlled, crossover trial of intravenous methotrexate with leucovorin rescue and combination of methotrexate and azathioprine; c) an open trial of i.v. cyclophosphamide (completed). The trial of apheresis has just been closed after 39 patients have completed it. Analysis of the results is underway. The trial of i.v. methotrexate and combination therapy continues, although patients with inclusion body myositis are no longer being entered because of poor results in the first 12 patients randomized.